Catalyst for hydrocarbon conversion and conversion process utilizing the same

ABSTRACT

A sulfated calcined solid catalyst is provided which comprises (1) oxide or hydroxide of Group III or Group IV, e.g. zirconium, metal, (2) oxide or hydroxide of Group V, Group VI or Group VII, e.g. manganese, metal and (3) oxide or hydroxide of Group VIII, e.g. iron, metal. In one embodiment of the invention, the catalyst is used to isomerize normal alkanes having 4 to 7 carbon atoms per molecule, to obtain high octane number blending components for motor fuel and/or valuable chemical intermediates.

This is a continuation of application Ser. No. 247,225, filed Sept. 21,1988, now U.S. Pat. No. 4,918,041.

This invention relates to novel catalysts suitable for varioushydrocarbon conversions including isomerization of C₄ to C₇ acyclichydrocarbons, alkylation of alkanes and alkylation of aromatics,dehydrogenation or partial oxidation of hydrocarbons and the conversionof alkenes and alcohols to ethers such as methyl tertiary butyl ether.

The invention also relates to novel catalytic isomerization processesemploying the catalysts of the invention. Current commercial operationsfor n-butane isomerization include aluminum chloride and noble metalcatalyzed processes. The aluminum chloride process, operated atrelatively low temperature, is subject to corrosion and spent catalystdisposal problems. The high temperature noble metal process is subjectto poisoning by sulfur and thus, added cost of feedstock pretreatment.Also, thermodynamic equilibrium limits the yield of isobutane frombutane, and the need for a large butane separation tower for the productadds to the plant cost.

To obtain higher yields of isobutane, other isomerization processes havebeen developed. Liquid superacids containing a strong protic acid and astrong Lewis acid have been disclosed (U. S. patents 3,708,553;3,766,286; 3,839,489; 3,855,346). Because of instability, thesecatalysts give less than stoichiometric yields of isobutane.

Solid, very strongly acidic materials suitable for catalyzinghydrocarbon reactions, for example the isomerization of n-butane, havebeen prepared in the prior art by treatment of zirconium oxides withsulfate ion, for example 1N sulfuric acid, and calcining the product at500° C. for three hours, as disclosed in (1) Hino et al "Reactions ofButane and Isobutane Catalyzed by Zirconium Oxide Treated With SulfateIon", Journal of the American Chemical Society, Oct. 10, 1979, pages6439-41. Solid superacids suitable for catalyzing skeletalisomerizations of butane and isobutane have been prepared by exposing H₄TiO₄ to 1N sulfuric acid and calcining in air at 500° C. , as disclosedin (2) Hino et al, "Reactions of Butane and Isobutane Catalysed byTitanium Oxide Treated with Sulphate Ion", J.S.C. Chem. Comm., 1979,pages 1148-9. (3) Hino et al, "Synthesis of Solid Superacid Catalystwith Acid Strength of H_(o) <-16.04" disclose a preparation similar tothat in reference (1) above, wherein Zr(OH)₄ obtained from differentsources was calcined at temperatures up to 650° C. , and found suitablefor reactions of butane in a recirculation reactor at 25° C.

In (4) Ito et al Japanese Pat. No. 61.242.641, solid acid catalysts forbutane alkylation are prepared by impregnating sulfate-containingmaterials and rare earth metals or their compounds or supportsconsisting of Group IV metal hydroxides or oxides, followed bycalcination and stabilization. Powdered Zr(OH)₄ supports wereimpregnated with lanthanum nitrate, dried, calcined at 300° C., treatedwith sulfuric acid, dried and calcined at 550° C. for 3 hours.

In (5) Japanese patent publication 87-344276/49, a solid superacidcatalyst was prepared by impregnating a carrier comprising the hydroxideor oxide of a Group III or Group IV metal with a Group VIII metal (theabstract refers to Group VII, but the examples given are of Group VIIImetals), for use in producing lower paraffin hydrocarbons from shaleoil.

In (6) Chemical Week, Nov. 25, 1987, the treatment of zirconium,titanium and iron oxides with sulfuric acids to produce "sulfated"inorganic oxides that show superior catalytic activity for alkylation ofortho-xylene by styrene, is disclosed.

In (7) Baba et al Japanese Pat. No. 61-2633932, November 21, 1986, filedMay 17, 1985, hydrocarbons are isomerized at reaction temperature below400° C. using a catalyst obtained by impregnating Group VIII metals,e.g. nickel, platinum, ruthenium, rhodium, palladium, osmium or iridium,and sulfate ion or precursor thereof in a carrier made of Group IVmetals, e.g. titanium, zirconium, hafnium, silicon, germanium or tin,and/or hydroxide or oxide of Group III metals, e.g. aluminum, gallium,indium and thallium, and stabilizing by roasting at 450-800° C. for 5 to16 hours.

In (8) Veda et al Japanese Pat. No. 62-246993, filed April 21, 1986,paraffin hydrocarbons are thermally cracked at 150-350° C. and over 50atmospheres hydrogen pressure in the presence of a solid, ultra stronglyacidic catalyst made by treating hydroxides or impregnating a Group VIIImetal, e.g. nickel, platinum, ruthenium, rhodium, palladium, osmium oriridium, on a supporting body of a hydroxide or oxide of Group III orGroup IV metals, e.g. titanium, zirconium, silicon, germanium, tin,aluminum, gallium or indium, followed by treating with sulfuric acid androasting to stabilize the catalyst.

References (7) and (8) indicate that addition of Group VIII metalimproves the catalytic activities of the solid superacids and that thesesolid superacids are suitable for isomerization of alkanes and xylenes,and cracking of shale oil or coal to light paraffins.

A solid superacid catalyst reported by (9) K. Arata et al, J. Amer.Chem. Soc., 101, 6439 (1979), a sulfuric acid treated zirconium oxide,isomerized n-butane at 100 to 250° C. , but the n-butane isomerizationbelow 1000C is negligible.

The present invention provides a sulfated, very strongly acidic catalystwhich contains, in addition to oxide or hydroxide of Group III or GroupIV element and Group VIII metal, as in reference (7) above, oxide orhydroxide of a Group V or Group VI or Group VII metal. A superiorcatalyst is thus obtained for use for example in the isomerization ofparaffin hydrocarbons.

The catalysts according to the invention comprise a sulfated andcalcined solid mixture of (1) oxide or hydroxide of metal from a firstclass consisting of Group III and Group IV metals, (2) oxide orhydroxide from a second class consisting of Group V, Group VI or GroupVII metal and (3) oxide or hydroxide of Group VIII metal. The weightratio of metal from the second class to Group VIII metal is in the rangefrom 0.1:1 to 2.0:1, preferably 0.2:1 to 1.0:1. The catalyst preferablycontains a major amount of oxide or hydroxide of metal from the firstclass and a minor amount, preferably in the range from 0.02 to 15.0weight percent, more preferably 0.1 to 4.5 weight percent, of totalmetal from the second class and Group VIII metal.

The carrier or support for the catalyst according to the invention is anoxide or hydroxide of a Group III or Group IV element. Examples ofsuitable such elements are aluminum, gallium, indium, thallium,titanium, zirconium, hafnium, silicon, germanium, tin and lead.Preferred are silicon, aluminum, zirconium and mixtures of two or morethereof.

Metals from Groups V, VI or VII which can be used according to theinvention include arsenic, antimony, bismuth, vanadium, niobium,tantalum, selenium, tellurium, chromium, molybdenum, tungsten, manganeseand rhenium and mixtures of two or more thereof.

Metals from Group VIII which can be used according to the inventioninclude iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium,iridium and platinum and mixtures of two or more thereof.

The catalysts according to the invention may be prepared for example byimpregnating a support of a Group III or Group IV metal oxide orhydroxide with an aqueous solution containing compounds of Group VII andGroup VIII metals. Alternatively the support can be impregnatedseparately with a solution of a Group VII metal compound and a solutionof a Group VIII metal compound.

The catalysts according to the invention may also be prepared byco-precipitation of solid hydroxides of (1) Group III or Group IVmetals, (2) Group V, Group VI or Group VII metals and (3) Group VIIImetals, from aqueous solutions containing compounds of such metals. Insuch method, the amount of the Group VIII metal hydroxide is typicallyin the range from 0.01 to 10.0 percent by weight of the totalprecipitated hydroxide. Mixtures of Group III and Group IV metal oxidesor hydroxides, or of two or more from among Group V, Group VI and GroupVII metal oxides or hydroxides, may be employed.

Solutions of metal compounds which can be used in the preparation ofcatalysts according to the invention, by impregnation orco-precipitation, are known in the art. For example, aqueous solution ofchloroplatinic acid or tetra-ammine-platinum complex can be used toincorporate platinum, in the catalyst. Nitrates of iron and of manganesecan be used for example to incorporate those metals in the catalyst.Solutions of zirconium oxychloride or of zirconyl nitrate can be usedfor example to prepare a zirconium support for the catalyst according tothe invention. Various other solutions can be employed as needed.

Sulfate ion may be supplied to the catalyst according to the inventionby treatment of the solid catalyst with sulfuric acid, for example0.01-10 N sulfuric acid, preferably 0.1-5 N sulfuric acid. Othercompounds such as ammonium sulfate capable of providing sulfate ion canbe employed. Compounds such as hydrogen sulfide or sulfur dioxide ormercaptans, capable of forming sulfate ions upon calcining, can also beemployed. Preferred catalysts for use according to the invention arethose which have been sulfated with ammonium sulfate.

The catalysts according to the invention contain substantial amounts ofsulfate ion, preferably in amount of 0.5 to 20 weight percent based ontotal catalyst, and more preferably 5 to 15 weight percent.

The catalysts according to the invention are calcined at a temperaturewhich is preferably in the range from 450-800° C., more preferably550-700° C., and for a period of time in the range from 2 to 30 hours.Combinations of temperature and time can be chosen in order to provide adesired degree of conversion. For example, calcining at 550° C. for 12hours provides about the same initial conversion of n-butane t isobutaneas calcining at 575° C. for 4 hours.

The catalysts according to the invention are in one embodiment of theinvention used to isomerize normal alkanes having four to seven carbonatoms, namely butane, pentane, hexane and heptane, to convert thestraight chain hydrocarbons into branched chain hydrocarbons havinghigher octane number for use as motor fuel or, as in the case of butane,having enhanced value as an intermediate for such products astertiarybutyl alcohol and high octane alkylates.

The isomerization is carried out by contacting the hydrocarbon feed withthe solid catalyst at temperatures in the range from 0° C. to 400° C.,preferably in the range from 20 to 150° C. and at pressure in the rangefrom 1 to 50 atmospheres. An advantage of the catalysts according to theinvention is that they are capable of providing higher yields of desiredproduct at a given temperature than the prior art catalysts, and it istherefore possible to obtain a given yield with the catalyst accordingto the invention at a lower temperature than that required with theprior art catalysts, and therefore with lesser heat requirements andexpense. The catalysts according to the invention also exhibit abeneficial degree of sulfur tolerance. The isomerization may beconducted either in the presence or absence of hydrogen. If conducted inthe presence of hydrogen, the mole ratio of hydrogen to hydrocarbon ispreferably in the range from 0.1:1 to 10:1. Inert gas such as nitrogen,helium, or argon may be employed. Generally, a temperature is used whichis sufficiently high to obtain a desired rate of reaction, but not sohigh as to result in unnecessarily great heat requirements.

EXAMPLE 1

A sulfated zirconia based catalyst containing the Group VIII metal,iron, and the Group VII metal, manganese, is prepared by the followingco-precipitation method:

Suitable amounts of zirconyl nitrate and ferric nitrate and manganesenitrate are dissolved in de-ionized water to make 1.0 liter of solution(A) of concentrations as hereinafter indicated. 130 grams ofconcentrated ammonium hydroxide are diluted with sufficient de-ionizedwater to make 1.0 liter of solution (B). 500 milliliters of de-ionizedwater are added to a 5 liter Morton flask. Solution (A) and solution (B)are added concurrently from two addition funnels to the Morton flaskslowly with rapid stirring. The pH of the resulting reaction mixture iskept at about 7.0. The reaction slurry is filtered and the filter cakeis washed with de-ionized water several times until the filtrate isnitrate free. The damp cake is applied to perforated plates, placed in atray and dried overnight at 150° C. The pellets are removed from thetray, transferred to a porcelain dish and calcined in an oven at 500° C.for 4.0 hours. The calcined pellets are added slowly to a beakercontaining 1.0 normal sulfuric acid solution at room temperature. Theamount of sulfuric acid is determined by the following ratio of 15milliliters of 1.0 normal sulfuric acid per gram of pellet. The sulfuricacid solution is decanted after the pellets are soaked for 2.0 hours.The pellets are calcined again at 500° C. for 4 hours.

EXAMPLES 2 TO 9

The catalysts prepared in Example 1 are used in isomerization ofn-butane as follows: In a fixed bed reactor containing 5.0 millilitersof solid catalyst, n-butane (2.2 milliliters of liquid per hour) andnitrogen (30 milliliters per minute) are continuously added from the topof the reactor. The reaction temperature is controlled by an oilcirculating heating jacket. The reaction pressure is controlled using aback pressure regulator. The reaction sample is taken from the bottom ofthe reactor (after the back pressure regulator) by withdrawing the gasmixture using a gas tight syringe. The degree of isomerization isdetermined on samples taken after two-hour reaction time, using a gaschromatograph equipped with a SE-30 capillary column. The results areshown in the following table:

                                      TABLE 1                                     __________________________________________________________________________    Isomerization of n-butane to isobutane (catalyst charge: 5.0                  milliliters;                                                                  n-butane feed; 2.2 milliliters of liquid per hour; nitrogen charge: 30        milliliters per minute).                                                      Run                   Isomerization                                                                          Product Composition (% wt)                     Example                                                                            No.                                                                              Catalyst      Temperature °C.                                                                 Isobutane                                                                            n-butane                                __________________________________________________________________________    2     1 Neat ZrO.sub.2                                                                              50       0.09   99.90                                         2 Neat ZrO.sub.2                                                                              75       0.11   99.89                                         3 Neat ZrO.sub.2                                                                              100      0.29   99.70                                   3     4 1.5% Ru on ZrO.sub.2                                                                        50       0.62   99.27                                         5 1.5% Ru on ZrO.sub.2                                                                        75       3.40   95.98                                         6 1.5% Ru on ZrO.sub.2                                                                        100      4.55   94.94                                   4     7 1.5% Fe on ZrO.sub.2                                                                        50       2.11   97.89                                         8 1.5% Fe on ZrO.sub.2                                                                        75       11.86  88.14                                         9 1.5% Fe on ZrO.sub.2                                                                        100      23.29  75.70                                   5    10 2.0% Fe on ZrO.sub.2                                                                        50       2.26   97.74                                        11 2.0% Fe on ZrO.sub.2                                                                        75       10.09  89.91                                        12 2.0% Fe on ZrO.sub.2                                                                        100      18.36  81.12                                   6    13 1.5% Fe, 0.5% Mn on ZrO.sub.2                                                               23       2.37   97.62                                        14 1.5% Fe, 0.5% Mn on ZrO.sub.2                                                               50       6.50   93.50                                        15 1.5% Fe, 0.5% Mn on ZrO.sub.2                                                               100      24.58  74.39                                   7    16 1.0% Fe, 1.0% Mn on ZrO.sub.2                                                               23       4.07   95.93                                        17 1.0% Fe, 1.0% Mn on ZrO.sub.2                                                               50       9.31   90.40                                        18 1.0% Fe, 1.0% Mn on ZrO.sub.2                                                               75       11.20  88.51                                   8    19 0.5% Fe, 1.5% Mn on ZrO.sub.2                                                               23       1.47   98.53                                        20 0.5% Fe, 1.5% Mn on ZrO.sub.2                                                               50       1.31   98.69                                        21 0.5% Fe, 1.5% Mn on ZrO.sub.2                                                               75       0.88   99.12                                   9    22 3.75 Fe, 1.25% Mn on ZrO.sub.2                                                              23       4.58   95.42                                        23 3.75 Fe, 1.25% Mn on ZrO.sub.2                                                              50       10.29  89.71                                        24 3.75 Fe, 1.25% Mn on ZrO.sub.2                                                              75       15.0   85.0                                         25 3.75 Fe, 1.25% Mn on ZrO.sub.2                                                              100       5.04  94.96                                   __________________________________________________________________________

The catalyst used in Example 2 above was zirconium without added GroupVIII metal. The catalyst used in Example 3 was zirconium with 1.5% addedruthenium, prepared as described in Example 1, but employing the GroupVIII metal, ruthenium, in place of iron. The catalysts used in Examples4 to 9 were zirconium with the indicated added amounts of iron, or ofiron and manganese, prepared as described in Example 1. All of thecatalysts in Examples 2 to 9 were sulfated and calcined as described inExample 1.

The following table presents data from the above Table 1 to show theeffect of varying catalyst composition on the isomerization results at agiven temperature:

    ______________________________________                                                                Isomeriz.                                             Run                     Temp.    Isobutane % in                               No.  Catalyst           °C.                                                                             Isomeriz. Prod.                              ______________________________________                                        11   2.0% Fe on ZrO.sub.2                                                                             75       10.09                                        12   2.0% Fe on ZrO.sub.2                                                                             100      18.36                                        15   1.5% Fe, 0.5% Mn on ZrO.sub.2                                                                    100      24.58                                        18   1.0% Fe, 1.0% Mn on ZrO.sub.2                                                                    75       11.20                                        21   0.5% Fe, 1.5% Mn on ZrO.sub.2                                                                    75        0.88                                        24   3.75% Fe, 1.25% Mn on ZrO.sub.2                                                                  75       15.00                                        25   3.75% Fe, 1.25% Mn on ZrO.sub.2                                                                  100       5.04                                        ______________________________________                                    

Comparison of Runs 12 and 15 shows the increase in isomerizationactivity by using Group VIII and Group VII metals together, in place ofthe same total amount of Group VIII metal. Runs 18 and 21 show theeffect of varying the ratio of Group VIII metal to Group VII metal inthe catalyst, and shows that unsatisfactory results are obtained whenthe ratio is 1:3. The ratio of Group VIII metal to Group VII metal maybe about 1 to 1 (as in Run 18) or somewhat lower with satisfactoryresults, but a ratio higher than 1 to 1 is preferred. Comparisons ofRuns 15 and 25 show that, at a ratio of Group VIII metal to Group VIImetal of 3 to 1, better results are obtained with total amount of GroupVIII and Group VII metal of 2.0 than with total amount of Group VIII andGroup VII metal of 5.0.

EXAMPLES 10-16

Sulfated zirconia based catalysts containing iron and manganese areprepared by a co-precipitation method similar to that of Example 1,except that ammonium sulfate, rather than sulfuric acid, is used tosulfate the catalyst, and the sulfation is done prior to any calciningof the catalyst. The dried pellets from the overnight drying step aretreated with ammonium sulfate to incorporate 4% or 8% of sulfate ion inthe catalyst, using incipient wetness technique, then calcined.

The catalysts in Examples 10 through 14 were precipitated at pH 7.0. Thecatalyst in Example 15 was precipitated at pH 4.0; the catalyst inExample 16 at pH 9.5. The catalysts in Examples 10, 11, 13, 15 and 16contained 4% sulfate ion; the catalysts in Examples 12 and 14, 8%sulfate ion. The catalysts in Examples 10, 11, 14, 15 and 16 werecalcined 16 hours at 600° C.; the catalyst in Example 12 was calcined 20hours at 625° C.; the catalyst in Example 13 was calcined 24 hours at600° C.

The catalysts are used in isomerization of n-butane by the proceduredescribed in Examples 2-9, with results as follows:

                                      TABLE 2                                     __________________________________________________________________________                                         PRODUCT                                         RUN               ISOMERIZATION                                                                             COMPOSITION (% WT)                       EXAMPLE                                                                              NO. CATALYST      TEMPERATURE °C.                                                                    ISOBUTANE                                                                             n-BUTANE                         __________________________________________________________________________    10     26  NEAT ZrO.sub.2                                                                              25           0.61   99.23                                   27  NEAT ZrO.sub.2                                                                              50           3.98   95.77                                   28  NEAT ZrO.sub.2                                                                              75          10.74   88.70                            11     29  1.5% Fe, 0.5% Mn on ZrO.sub.2                                                               25           1.67   98.25                                   30  1.5% Fe, 0.5% Mn on ZrO.sub.2                                                               50          34.11   64.54                                   31  1.5% Fe, 0.5% Mn on ZrO.sub.2                                                               75          44.29   53.02                            12     32  1.5% Fe, 0.5% Mn on ZrO.sub.2                                                               25           3.26   96.50                                   33  1.5% Fe, 0.5% Mn on ZrO.sub.2                                                               50          35.75   62.78                                   34  1.5% Fe, 0.5% Mn on ZrO.sub.2                                                               75          51.34   43.55                            13     35  1.5% Fe, 0.5% Mn on ZrO.sub.2                                                               25           3.14   96.59                                   36  1.5% Fe, 0.5% Mn on ZrO.sub.2                                                               50          28.27   70.71                                   37  1.5% Fe, 0.5% Mn on ZrO.sub.2                                                               75          55.08   40.25                            14     38  1.5% Fe, 0.5% Mn on ZrO.sub.2                                                               25           0.76   99.24                                   39  1.5% Fe, 0.5% Mn on ZrO.sub.2                                                               50          13.42   86.35                                   40  1.5% Fe, 0.5% Mn on ZrO.sub.2                                                               75          40.69   57.55                            15     41  1.5% Fe, 0.5% Mn on ZrO.sub.2                                                               25           1.02   98.95                                   42  1.5% Fe, 0.5% Mn on ZrO.sub.2                                                               50          17.89   81.32                                   43  1.5% Fe, 0.5% Mn on ZrO.sub.2                                                               75          37.96   59.62                            16     44  1.5% Fe, 0.5% Mn on ZrO.sub.2                                                               25           1.70   98.30                                   45  1.5% Fe, 0.5% Mn on ZrO.sub.2                                                               50          26.05   73.12                                   46  1.5% Fe, 0.5% Mn on ZrO.sub.2                                                               75          45.57   51.64                            __________________________________________________________________________

Other suitable embodiments of the invention are obtained when otherelements, or mixtures thereof, from Group III or Group IV are used inplace of zirconium, when other metals or mixtures thereof from Group V,Group VI or Group VII are used in place of manganese, and when otherGroup VIII metals are used in place of iron.

The invention claimed is:
 1. Method of isomerizing a feedstockcomprising acyclic hydrocarbons having 4 to 7 carbon atoms per moleculewhich comprises contacting said feedstock at a temperature in the rangefrom 0 to 400° C., and a pressure in the range from 1 to 50 atmosphereswith a solid mixture of (1) oxide or hydroxide of element from a firstclass consisting of Group III or Group IV elements, (2) oxide orhydroxide of metal from a second class consisting of Group V, Group VIor Group VII metals, and (3) oxide or hydroxide of Group VIII metals,the ratio of metal from said second class to Group VIII metal being inthe range from 0.1:1 to 2.0:1.
 2. Method according to claim 1 whereinthe contacting is in the presence of hydrogen.
 3. Method according toclaim 1 wherein the contacting is in the absence of hydrogen.